Hyperoxia, hypocapnia and hypercapnia: useful predictors in paediatric cardiac arrest?

This prospective multi-centre study enrolled patients aged between one month and 18 years who achieved return of spontaneous circulation (ROSC) after in-hospital cardiac arrest and had arterial blood gas (ABG) analysis performed at ROSC and 24 hours post event. Treating clinicians completed case report forms including details such as patient demographics, cause of the arrest, first recorded electrocardiogram, staff undertaking resuscitation, ventilator support, drug administration, duration of arrest, and ABG results.

Hyperoxia was defined as a PaO2 of ≥ 300 mmHg and hypoxia as a PaO2 < 60 mmHg. Corresponding values for hypercapnia and hypocapnia were PaCO2 < 30 mmHg and PaCO2 ≥ 50 mmHg. The primary outcome measure was in-hospital mortality. A secondary analysis of the data was also performed substituting PaO2 cut off points of 200 mmHg and then 100 mmHg.

A total of 543 cases of inhospital cardiac arrest were registered during the study period, with ROSC achieved in 71 % (386) of cases. ABG data were available for 223 patients, of whom 8.5 % (19) were classified as hyperoxic and 26.5 % (59) as hypoxic. Mortality was higher in patients with hyperoxia immediately after ROSC than those with normoxia (52.6 % vs 40.7 %) or those with hypoxia (42.4 %), although this failed to reach statistical significance (P=0.61). No significant differences in mortality were observed at 24 hours between patients with hyperoxia (33 %), hypoxia (29.8 %) or normoxia (35.8 %).